The present invention relates to a process for selectively fractionating branched dextrin and linear oligosaccharides from a starch-saccharified solution and utilizing the specific properties of the branched dextrin in food products.
Formerly, a process was established for fractionally producing maltose of a high purity and beta-limit dextrin (branched dextrin), which comprises the steps of reacting beta-amylase with liquefied starch, thereby forming a saccharified solution consisting mainly of maltose and beta-limit dextrin, and then contacting the thus saccharified solution with an OH-type anion exchange resin; see Japanese Patent Publication (KOKOKU) No. 46290/1977.
Maltose is a disaccharide formed by the alpha-1,4-linkage of two molecules of D-glucose and since maltose is lower in sweetness as compared to sucrose and D-glucose, it is broadly utilized as a sweetness-decreasing agent in the field of food fabrication. On the other hand, beta-limit dextrin is a macromolecule having a branched molecular structure and is referred to as branched dextrin. Due to its molecular structure, beta-limit dextrin is easily soluble into water in spite of being a macromolecule, it has a high viscosity, is stable and is not retrogradated. Accordingly, beta-limit dextrin has attracted attention as a raw material for fabricating food products because it imparts elasticity to food products and is good in preserving moisture in the food products, i.e., is a humectant.
However, there is a recent demand for a material lower in sweetness than maltose and concerning branched dextrin, the physical properties of a material which has a lower molecular weight than beta-limit dextrin, have been requested by food processors and others.
Starch consists of both linear-structural amylose formed by polymerization of D-glucose through alpha-1,4-linkages and branched-structural amylopectin of which the main body is polymerized through alpha-1,4-linkages and the remaining moiety is branched through the alpha-1,6-linkage at various places of the main body.
In the case where beta-amylase is reacted with a liquefied solution of starch having the structure noted above, since only the linear-structural amylose and the outer branches of the branched-structural amylopectin become the target of the attack of beta-amylase and the internal structure is not destroyed, maltose and macromolecular branched dextrin are obtained. See Japanese Patent Publication (KOKOKU) No. 46290/1977. However, in the case where alpha-amylase is reacted with starch, not only amylose but also the alpha-1,4-linkages of the internal structure of amylopectin are cleaved randomly and the alpha-1,6-linkages are not attacked. Accordingly, as a result, a saccharified solution of the linear oligosaccharides which are higher in degree of polymerization than maltose and branched dextrin which is lower in molecular weight than beta-limit dextrin are obtained.
As a result of the present inventors' studies, the inventors have noticed the above-mentioned facts, from the viewpoint that if a process of selectively fractionating the linear oligosaccharides which are higher in degree of polymerization than maltose and the branched dextrin which is lower in molecular weight than beta-limit dextrin from a saccharified solution of starch (which solution comprises the linear oligosaccharides and the branched dextrin) can be offered in order to simultaneously satisfy the above-mentioned recent demands in the market, it is possible to answer these recent market demands and, accordingly, the range of application of such linear oligosaccharides and branched dextrin to food products would be remarkably enlarged.
In Japanese Patent Publication (KOKOKU) No. 46290/1977 noted above, maltose and macromolecular beta-limit dextrin can be separated effectively from a saccharified solution of maltose and beta-limit dextrin utilizing the adsorptive property of maltose to an OH-type anion exchange resin. However, a saccharified solution resulting from the degradation of starch with alpha-amylase containing branched dextrin and linear oligosaccharides, it has been found that there is no difference between the absorptive properties of the linear oligosaccharides and that of the branched dextrin to an OH-type anion exchange resin. This means that the two substances cannot be effectively separated with an OH-type anion exchange resin.
Thus, it is a problem to fractionate the above-mentioned branched dextrin and linear oligosaccharides respectively from the saccharified solution containing the two.
As a result of the present inventors' studies fractionating branched dextrin and linear oligosaccharides from a degradation product of starch by alpha-amylase, the inventors have found that differences are caused between the internal invasions to a gel-filtrating agent or between the sliding speeds on the surface, depending upon the difference between the linear molecular structure of the oligosaccharides and the branched molecular structure of the dextrin in the degradation product of starch. Utilizing these differences, the present inventors have succeeded in effectively fractionating the branched dextrin and linear oligosaccharides respectively from a saccharified solution of the degradation product of starch.
Accordingly, an object of the present invention is to provide a process for effectively and selectively fractionating branched dextrin and linear oligosaccharides from a saccharified solution which has been obtained by applying alpha-amylase to starch and consists mainly of the branched dextrin and the linear oligosaccharides, and at the same time, in offering a method for utilizing the thus fractionated products for food products based on the physical properties of the resulting fractionated products.
The present invention will be explained in detail as follows.